The present invention relates to an improvement of operating apparatuses for switchgears like circuit breakers used as electric power switching devices installed in an electric power substation or in a switching station, for example.
A conventionally available operating apparatus for a circuit breaker, which is a typical example of switchgears, utilizes an elastic force exerted by a spring as an operating force. FIGS. 32-35 show a conventional operating apparatus for a circuit breaker disclosed in Japanese Laid-open Patent Publication No. 63-304542, in which FIG. 32 is a perspective view generally showing the construction of the operating apparatus for the circuit breaker, and FIG. 33 is a constructional diagram of the operating apparatus for the circuit breaker of FIG. 32 showing a state in which the circuit breaker is closed and torsion bars 29, 35, 28, 34 for making and breaking a circuit are all energized (caused to store elastic restoring energy by twisting).
FIG. 34 is a constructional diagram of the operating apparatus for the circuit breaker of FIG. 32 showing a state in which the circuit breaker is opened, the circuit-breaking torsion bars 28, 34 are deenergized (caused to release elastic restoring energy by restoring the original shape), and the circuit-making torsion bars 29, 35 are energized. FIG. 35 is a constructional diagram of the operating apparatus for the circuit breaker of FIG. 32 showing a state in which the circuit breaker is closed, the circuit-breaking torsion bars 28, 34 are energized and the circuit-making torsion bars 29, 35 are deenergized.
In these Figures, designated by the numeral 1 is a housing, designated by the numeral 24 is cylindrical body fixed to the housing 1, and designated by the numerals 26 and 27 are rotatable levers fitted to pins (not shown) provided on an end surface of the cylindrical body 24. Since the circuit-breaking torsion bars 28, 34 are energized when the circuit-making torsion bars 29, 35 are deenergized, the amount of energy stored in the circuit-making torsion bars 29, 35 is made larger than the amount of energy stored in the circuit-breaking torsion bars 28, 34. One end of the circuit-breaking torsion bar 28 is fixed to the housing 1 while the other end of the circuit-breaking torsion bar 28 is fixed to the lever 26. Also, one end of the circuit-breaking torsion bar 34 is fixed to a rotary shaft 32 while the other end of the circuit-breaking torsion bar 34 is fixed to the lever 26 as shown in FIG. 32.
On the other hand, one end of the circuit-making torsion bar 29 is fixed to the housing 1 while the other end of the circuit-making torsion bar 29 is fixed to the lever 27. Also, one end of the circuit-making torsion bar 35 is fixed to a rotary shaft 33 while the other end of the circuit-making torsion bar 35 is fixed to the lever 27 as shown in FIG. 32. Referring to FIG. 33, designated by the numeral 37 is a closing lever fixed to the rotary shaft 33. A counterclockwise turning force is exerted on the closing lever 37 by the circuit-making torsion bars 29, 35 through the rotary shaft 33. It is to be noted that the direction of rotation, as well as horizontal and vertical directions, is expressed as they appear in the relevant Figures unless otherwise mentioned in the following discussion.
Referring again to FIG. 33, designated by the numeral 2 is a cam shaft rotatably supported by the housing 1, designated by the numeral 3 is a cam which is fixed to the cam shaft 2 and rotates together with the cam shaft 2, designated by the numeral 13 is a pin provided on the cam 3, and designated by the numeral 14 is a closing latch engaged with the pin 13. Further, designated by the numeral 15 is a closing trigger meshed with the closing latch 14, and designated by the numeral 16 is a closing electromagnet having a plunger 17. Designated by the numeral 38 is a rotary shaft which is rotatably supported by the housing 1 and turned counterclockwise by an electric motor (not shown), designated by the numeral 39 is a small gear wheel which is fixedly mounted on the rotary shaft 38, and designated by the numeral 40 is a large gear wheel which is fixedly mounted on the cam shaft 2 and engaged with the small gear wheel 39. The large gear wheel 40 lacks teeth on one part of its periphery such that the large gear wheel 40 becomes disengaged from the small gear wheel 39 when the circuit-making torsion bars 29, 35 are energized.
In FIG. 33, designated by the numeral 41 is a link which connects the closing lever 37 and the large gear wheel 40 to each other via pins provided on the closing lever 37 and the large gear wheel 40. Designated by the numeral 36 is an interrupting lever fixedly mounted on the rotary shaft 32 on which a counterclockwise turning force is exerted by the circuit-breaking torsion bars 28, 34 via the rotary shaft 32. Designated by the numeral 8 is a pin provided on the interrupting lever 36, and designated by the numeral 9 is a rotary member provided on the interrupting lever 36. Designated by the numeral 18 is a tripping latch meshed with the pin 8, wherein a clockwise turning force is exerted on the tripping latch 18 by a spring 43.
Designated by the numeral 19 is a tripping trigger meshed with the tripping latch 18, and designated by the numeral 20 is a tripping electromagnet having a plunger 21. The plunger 21 is driven rightward as illustrated in FIG. 33 when the tripping electromagnet 20 is excited, and the plunger 21 is caused to return to its original position by a reset spring (not shown) when the tripping electromagnet 20 is deenergized. Designated by the numeral 10 is an on-off switch having a stationary contact 12 and a movable contact 22. The movable contact 22 is connected to the interrupting lever 36 via a link mechanism 23 and a rod 61. Designated by the numeral 42 is a shock absorber connected to the interrupting lever 36 to alleviate shocks occurring when the movable contact 22 goes into contact with and comes apart from the stationary contact 12.
Now, circuit-breaking and making operations of the aforementioned conventional operating apparatus for the circuit breaker are described, beginning with the circuit-breaking operation below.
Referring to FIG. 33, the interrupting lever 36 continuously receives the counterclockwise turning force exerted by the circuit-breaking torsion bars 28, 34, and this turning force is carried by the tripping trigger 19 via the tripping latch 18. If the tripping electromagnet 20 is excited in this condition, the plunger 21 moves rightward, causing the tripping trigger 19 to turn clockwise and become disengaged from the tripping latch 18. At this time, the tripping latch 18 is caused to turn counterclockwise by a reaction force exerted by the pin 8 and become released from the pin 8. When the tripping latch 18 and the pin 8 are disengaged, the interrupting lever 36 turns counterclockwise, causing the movable contact 22 to move in a circuit-breaking direction and become separated from the stationary contact 12. Shown in FIG. 34 is the state in which the above-described circuit-breaking operation has been completed.
The circuit-making operation from the state shown in FIG. 34 is carried out as described below. In FIG. 34, the cam 3 fixed to the cam shaft 2 is connected to the closing lever 37 via the cam shaft 2, the large gear wheel 40 fixed to the cam shaft 2 and the link 41, and a clockwise turning force is exerted on the cam 3 by the circuit-making torsion bars 29, 35. This turning force is carried by the closing trigger 15 via the closing latch 14.
If the closing electromagnet 16 is excited in this condition, the plunger 17 moves rightward and hits against the closing trigger 15, causing the closing trigger 15 to turn clockwise and become disengaged from the closing latch 14. At this time, the closing latch 14 is caused to turn counterclockwise by a reaction force exerted by the pin 13 and become released from the pin 13. When the closing latch 14 and the pin 13 are disengaged, the large gear wheel 40 and the cam 3, on which the clockwise turning force is exerted by the circuit-making torsion bars 29, 35, turn clockwise and push the rotary member 9 provided on the interrupting lever 36 upward, so that the interrupting lever 36 is caused to turn clockwise. As the interrupting lever 36 turns clockwise in this way, the circuit-breaking torsion bars 28, 34 are twisted and store elastic restoring energy. At the same time, the clockwise turn of the interrupting lever 36 causes the movable contact 22 to move in a circuit-making direction.
When the interrupting lever 36 turns clockwise by a specific angle, the tripping latch 18 meshes with the pin 8 and the tripping trigger 19 engages with the tripping latch 18. The cam 3 further turns clockwise while pushing against the interrupting lever 36 via the rotary member 9 until the tripping latch 18 and the pin 8, and the tripping trigger 19 and the tripping latch 18, engage with each other in a stable fashion. The cam 3 is eventually released from the rotary member 9 and goes into a position shown in FIG. 35. Shown in FIG. 35 is the state in which the above-described circuit-making operation has been completed, where the circuit-breaking torsion bars 28, 34 are energized, the pin 8 is locked by the tripping latch 18 and the circuit-making torsion bars 29, 35 are deenergized.
The circuit-making torsion bars 29, 35 are energized (caused to store elastic restoring energy by twisting) from the state shown in FIG. 35 in a manner described below. The circuit-making torsion bars 29, 35 are deenergized immediately upon completion of the aforementioned circuit-making operation as shown in FIG. 35. As the small gear wheel 39 is turned counterclockwise by the earlier-mentioned electric motor (not shown), the large gear wheel 40 turns clockwise. As a result, the closing lever 37 connected to the link 41 turns clockwise and the circuit-making torsion bars 29, 35 are energized (twisted) via the rotary shaft 33.
As the large gear wheel 40 turns clockwise, the direction of tensile load exerted on the link 41 approaches a dead point where the direction of the tensile load intersects the central axis of the cam shaft 2. When the direction of the tensile load just goes beyond this dead point, the large gear wheel 40, or the cam shaft 2, receives the clockwise turning force exerted by the circuit-making torsion bars 29, 35 via the link 41 and, at the same time, the small gear wheel 39 and the large gear wheel 40 are disengaged because the large gear wheel 40 lacks teeth on one part of its periphery. Therefore, even if the electric motor continues to run, the large gear wheel 40 remains stationary (without rotating) at a position where it is disengaged from the small gear wheel 39. Then, the pin 13 meshes with the closing latch 14 and the clockwise turning force exerted on the large gear wheel 40 due to twisting force of the circuit-making torsion bars 29, 35 is maintained, whereby storage of elastic restoring energy in the circuit-making torsion bars 29, 35 is completed. The conventional operating apparatus for the circuit breaker returns to the state shown in FIG. 33 in the aforementioned manner.
In the above-described conventional operating apparatus for the circuit breaker, the circuit-making torsion bars 29, 35 are energized (twisted) by the closing lever 37 and the link 41 connected to the large gear wheel 40. In this operating apparatus, torque to be produced by the electric motor for twisting the circuit-making torsion bars 29, 35 increases as the torsion bars 29, 35 approach their final energizing stage. For this reason, it is necessary that components of the electric motor and the operating apparatus, such as the large gear wheel 40, the link 41, the closing lever 37, have high strength. In addition, since the large gear wheel 40 is used as a crank with the link 41 connected to the large gear wheel 40, the large gear wheel 40 should have a large diameter.
To overcome the aforementioned problems, Japanese Laid-open Utility Model Publication No. 56-165319 discloses a different type of operating apparatus, in which a cam rotating with a large gear wheel is fixedly mounted on a rotary shaft of the large gear wheel, and a spring for making a circuit is energized by means of this cam. If the shape of the cam is properly designed, this operating apparatus makes it possible to avoid an increase in torque of an electric motor for driving the large gear wheel even at a final stage of energizing circuit-making torsion bars 29, 35 and achieve a reduction in size of an energizing mechanism.
This alternative arrangement of the prior art is now described in detail. FIGS. 36-39 show a conventional operating apparatus for a circuit breaker in which elastic restoring energy is stored by using the aforementioned type of cam. FIG. 36 is a perspective view generally showing the construction of the operating apparatus for the circuit breaker, FIG. 37 is a constructional diagram of the operating apparatus for the circuit breaker of FIG. 36 showing a state in which the circuit breaker is closed and torsion bars 29, 35, 28, 34 for making and breaking a circuit are all energized (caused to store elastic restoring energy by twisting), FIG. 38 is a constructional diagram of the operating apparatus for the circuit breaker of FIG. 36 showing a state in which the circuit breaker is opened, the circuit-breaking torsion bars 28, 34 are deenergized (caused to release elastic restoring energy by restoring the original shape), and the circuit-making torsion bars 29, 35 are energized, and FIG. 39 is a constructional diagram of the operating apparatus for the circuit breaker of FIG. 36 showing a state in which the circuit breaker is closed, the circuit-breaking torsion bars 28, 34 are energized and the circuit-making torsion bars 29, 35 are deenergized.
In these Figures, elements identical or equivalent to those shown in FIGS. 32-35 are designated by the same reference numerals and a description of such elements is omitted here. Compared to the construction of FIGS. 32-35, the circuit-making torsion bar 35 and a rotary shaft 33 are provided at different positions, although one end of the circuit-making torsion bar 35 is fixed to the rotary shaft 33 and the other end of the circuit-making torsion bar 35 is fixed to a lever 27 in similar fashion (FIG. 32). The circuit-making torsion bars 29, 35 exerts a clockwise turning force (as illustrated in FIG. 37) on a closing lever 37 which is fixedly mounted on the rotary shaft 33. While the counterclockwise turning force is exerted on the closing lever 37 in FIG. 32, the clockwise turning force is exerted on the closing lever 37 in FIG. 37. Although the direction of the turning force differs from each other, the same operational and working effects are obtained.
In FIGS. 36-39, designated by the numeral 2 is a cam shaft rotatably supported by a housing 1, designated by the numeral 3 is the aforementioned cam which is fixed to the cam shaft 2, designated by the numeral 5 is a pin provided on the cam 3, designated by the numeral 6 is a pin provided on the closing lever 37, and designated by the numeral 41 is a link. The closing lever 37 and the cam 3 are connected to the link 41 via the pins 5, 6. Designated by the numeral 7 is a second rotary member mounted on a common axis with the pin 6. Twisting force of the circuit-making torsion bars 29, 35 is transmitted to the cam 3 via the rotary shaft 33, the closing lever 37, the pin 6, the link 41 and the pin 5. Designated by the numeral 25 is a rotary shaft for rotatably supporting a closing trigger 15, designated by the numeral 98 is a rotary shaft for rotatably supporting a tripping trigger 19, and designated by the numeral 75 is a rotary shaft for rotatably supporting a tripping latch 18. These rotary shafts 25, 75, 98 are not assigned any reference numerals in the earlier-described conventional operating apparatus of FIG. 32.
Designated by the numeral 4 is a rotary shaft rotatably supported by the housing 1, and designated by the numeral 48 is a closing latch which is supported by the rotary shaft 4 in such a manner that it can rotate independently of the rotary shaft 4. The closing latch 48 continuously receives a counterclockwise turning force exerted by a spring (not shown) and engages with the pin 6. Designated by the numeral 49 is a pin provided on the closing latch 48. The closing latch 48 is locked by the closing trigger 15 via the pin 49. Designated by the numeral 45 is a small gear wheel which is rotatably supported by the housing 1 and rotated by an electric motor (not shown), and designated by the numeral 46 is a large gear wheel fixedly mounted on the rotary shaft 4. The large gear wheel 46 is engaged with the small gear wheel 45 and turned thereby.
Since maximum load required for storing elastic restoring energy in, or twisting, the circuit-making torsion bars 29, 35 is small for reasons described later, the diameters of the small gear wheel 45 and the large gear wheel 46 may be smaller than the small gear wheel 39 and the large gear wheel 40 of the conventional operating apparatus of FIG. 33, respectively. Designated by the numeral 50 is a second cam which is fixedly mounted on the rotary shaft 4 and rotates together with the large gear wheel 46. The small gear wheel 45, the large gear wheel 46, the second cam 50, the second rotary member 7, the closing lever 37, the closing latch 48, the closing trigger 15, a closing electromagnet 16 and a plunger 17 together constitute an energizing mechanism 30.
Now, circuit-breaking and making operations of this conventional operating apparatus for the circuit breaker are described, beginning with the circuit-breaking operation below.
Referring to FIG. 37, an interrupting lever 36 continuously receives a counterclockwise turning force exerted by the circuit-breaking torsion bars 28, 34, and this turning force is carried by the tripping trigger 19 via the tripping latch 18. If a tripping electromagnet 20 is excited in this condition, a plunger 21 moves rightward, causing the tripping trigger 19 to turn clockwise about the rotary shaft 98 and become disengaged from the tripping latch 18. At this time, the tripping latch 18 is caused to turn counterclockwise by a reaction force exerted by a pin 8 provided on the interrupting lever 36 and become released from the pin 8. When the tripping latch 18 and the pin 8 are disengaged, the interrupting lever 36 turns counterclockwise, causing a movable contact 22 of an on-off switch 10 to move in a circuit-breaking direction and become separated from its stationary contact 12. Shown in FIG. 38 is the state in which the above-described circuit-breaking operation has been completed.
The circuit-making operation from the state shown in FIG. 38 is carried out as described below. In FIG. 38, the cam 3 is connected to the closing lever 37 via the link 41, and the circuit-making torsion bars 29, 35 exerts a clockwise turning force on the closing lever 37 via the rotary shaft 33. This turning force is carried by the closing trigger 15 via the closing latch 48. If the closing electromagnet 16 is excited in this condition, the plunger 17 moves upward and hits against the closing trigger 15, causing the closing trigger 15 to turn counterclockwise about the rotary shaft 25. When the closing trigger 15 turns counterclockwise in this fashion, the closing latch 48 is caused to turn clockwise by a reaction force exerted by the pin 49 and become released from the pin 6.
When the pin 6 is released from the closing latch 48, the closing lever 37 turns clockwise and the cam 3 connected to the closing lever 37 via the link 41 turns clockwise about the cam shaft 2, thereby pushing a rotary member 9 provided on the interrupting lever 36 upward. This causes the interrupting lever 36 to turn clockwise and, as a consequence, the circuit-breaking torsion bars 28, 34 are twisted and store elastic restoring energy. At the same time, the clockwise turn of the interrupting lever 36 causes the movable contact 22 to move in a circuit-making direction. When the interrupting lever 36 turns clockwise by a specific angle, the tripping latch 18 meshes with the pin 8 and the tripping trigger 19 engages with the tripping latch 18.
The cam 3 further turns clockwise while pushing against the interrupting lever 36 via the rotary member 9 until the tripping latch 18 and the pin 8, and the tripping trigger 19 and the tripping latch 18, engage with each other in a stable fashion. The cam 3 eventually comes off the rotary member 9 and goes into a position shown in FIG. 39. Shown in FIG. 39 is the state in which the above-described circuit-making operation has been completed, where the circuit-breaking torsion bars 28, 34 are energized and the circuit-making torsion bars 29, 35 are deenergized.
In this operating apparatus for the circuit breaker, there are two cases in the circuit-breaking operation. These are a case where the circuit breaker breaks the circuit from the state shown in FIG. 39, and a case where the circuit breaker rebreaks the circuit immediately upon completion of the circuit-making operation. This circuit-rebreaking operation is performed as follows. If a circuit-rebreaking command is received when the circuit-making torsion bars 29, 35 have not been energized yet after deenergizing, the tripping electromagnet 20 is actuated and, as a consequence, the circuit-breaking torsion bars 28, 34 are deenergized and the on-off switch 10 is opened. At this point, the circuit breaker is opened, and the circuit-making torsion bars 29, 35 and the circuit-breaking torsion bars 28, 34 are all deenergized.
Storage of elastic restoring energy in the circuit-making torsion bars 29, 35 is performed as follows. Immediately upon completion of the circuit-making operation, the closing lever 37 is in a position rotated clockwise as shown in FIG. 39 from the state of FIG. 37, and the circuit-making torsion bars 29, 35 are deenergized. The circuit-making torsion bars 29, 35 are energized from the state shown in FIG. 39, for example. When the electric motor is run, the small gear wheel 45 turns clockwise and the large gear wheel 46 meshed with the small gear wheel 45 turns counterclockwise. Thus, the second cam 50 fixed to the large gear wheel 46 also turns counterclockwise.
When the second cam 50 reaches a specific position after turning counterclockwise, the second cam 50 comes into contact with the second rotary member 7 which is provided on the closing lever 37 and further turns counterclockwise, causing the closing lever 37 and the rotary shaft 33 to rotate counterclockwise. As a result of this counterclockwise rotation of the closing lever 37, the circuit-making torsion bars 29, 35 are twisted, or energized, via the rotary shaft 33.
Pushed by the second cam 50, the closing lever 37 further turns counterclockwise. When the closing lever 37 reaches a point slightly beyond its locking position with the closing latch 48, the second cam 50 separates from the second rotary member 7. When the second cam 50 has separated from the closing lever 37 (second rotary member 7), the closing lever 37 reversely turns clockwise due to the turning force exerted by the circuit-making torsion bars 29, 35 and is locked by the closing latch 48 via the pin 6 at the aforementioned locking position. At the same time, the closing trigger 15 meshes with the pin 49 provided on the closing latch 48. Consequently, the clockwise turning force exerted on the closing lever 37 by the circuit-making torsion bars 29, 35 is sustained by the closing latch 48 and the closing trigger 15, and storage of elastic restoring energy in the circuit-making torsion bars 29, 35 is finished at this point.
At the point where the circuit-making torsion bars 29, 35 have been energized and the closing lever 37 has reached the locking position with the closing latch 48, the closing lever 37 is actuated by pressing an unillustrated lever switch to open the circuit, and power supply to the electric motor is interrupted. The electric motor continues to turn counterclockwise for a while due to inertia and stops while the second cam 50 also continues to turn counterclockwise for a while and stops. Under conditions in which the closing lever 37 has been locked by the closing latch 48, the aforementioned unillustrated lever switch maintains an open-circuit state. The operating apparatus returns to the state shown in FIG. 37 in the above-described manner.
Since the second cam 50 is used to energize the circuit-making torsion bars 29, 35 by twisting them, the second cam 50 is properly shaped such that torques exerted on the electric motor and the large gear wheel 46 would not become too large even at a final stage of energizing the circuit-making torsion bars 29, 35. More specifically, the second cam 50 has a cam surface which produces a generally constant torque from the beginning to the final stage of energizing the circuit-making torsion bars 29, 35. This makes it possible to reduce the sizes of the electric motor, the small gear wheel 45 and the large gear wheel 46.
In the operating apparatus for the circuit breaker in which the second cam 50 is used for energizing the circuit-making torsion bars 29, 35 as described above, the second cam 50 overruns counterclockwise before it stops, due to inertial turning of the electric motor, after the circuit-making torsion bars 29, 35 have been energized and the power supply to the electric motor has been interrupted. The angle of overrun of the second cam 50 due to the inertial turning of the electric motor varies with the amount of frictional resistance, which is affected by such factors as the sizes of components of the energizing mechanism and the viscosity of lubricating oil. The frictional resistance also varies with temperature changes and the lapse of time. Therefore, the position where the second cam 50 stops is not definitely fixed. Rather, the second cam 50 is likely to stop before it reaches a specific angular range of rotation, or overrun that range.
If the second cam 50 stops before it reaches the specific angular range, that is, on the clockwise side of the desired stopping range, the closing lever 37 might hit against the second cam 50 when the closing lever 37 locked by the closing latch 48 is released for closing the on-off switch 10 and energizing the circuit-breaking torsion bars 28, 34. Should this happen, it is likely that the circuit-breaking operation is interrupted halfway. Also, an intense shock occurs when the closing lever 37 hits against the second cam 50.
As stated earlier, the power supply to the electric motor is interrupted by pressing unillustrated lever switch to open the circuit when the closing lever 37 has reached the locking position with the closing latch 48. To enable the closing lever 37 to engage with the closing latch 48, it is necessary to allow the closing lever 37 to overrun, or turn counterclockwise, slightly beyond its locking position with the aid of the inertia of the electric motor. If the amount of this overrun is too large, a correspondingly large amount of energy is required. Therefore, if the closing lever 37 is to be overrun with the aid of the inertia of the electric motor, it is necessary that the amount of overrun be sufficiently small so that the electric motor would not come to a halt halfway during its overrunning, and the individual components should be manufactured with high mechanical accuracy, resulting in an eventual cost increase.
Although it might be possible to employ an electric motor provided with a brake such that the second cam 50 can be stopped within the desired stopping range, this approach also results in a cost increase.
In view of the foregoing problems of the prior art, it is an object of the invention to provide a lightweight, low-cost operating apparatus for a switchgear.
According to the invention, an operating apparatus for a switchgear comprises an on-off switch driver including a rotatably mounted energizing lever linked to an on-off switch of the switchgear and an energy-storing device linked to the energizing lever, a retaining device including a locking lever, and an energizing mechanism including a cam turned by an electric motor in a specific direction, a current interrupter and a braking device, wherein the cam of the energizing mechanism turning in the specific direction begins to maintain contact with the energizing lever at a first angular position, turns the energizing lever in its energizing direction to energize the energy-storing device, causes the locking lever of the retaining device to lock the energizing lever such that the energizing lever remains in its energized condition without turning opposite to the energizing direction, and becomes separated from the energizing lever by further turning in the specific direction, the current interrupter is actuated and interrupts an electric current supplied to the electric motor when the cam reaches a second angular position after turning by a first specific angle from the first angular position, and the braking device brakes the cam when the cam reaches a third angular position after turning by a second specific angle from the second angular position due to inertial turning of the electric motor, whereby the cam stops within a specific angular range of rotation.
As the cam is forcibly braked by the braking device in this operating apparatus, it is possible to decrease variations in the amount of overrun of the cam, which could occur due to variations in the amount of frictional resistance caused by temperature changes or property changes with the lapse of time, and halt the cam such that the orientation of the cam falls within the specific angular range of rotation. This makes it possible to prevent shocks which could occur if the energizing lever collides with the cam when the energy-storing device is deenergized and the energizing lever turns opposite to its energizing direction. This serves to make the operating apparatus compact and inexpensive.
Furthermore, since the cam is braked by the braking device when the electric motor is in its final stage of inertial turning and its inertial energy has declined, energy required for braking is small and, therefore, the braking device may be of a simple structure. This also serves to make the operating apparatus compact and inexpensive.
In one aspect of the invention, the retaining device further includes an energizing lever deactivator which prohibits the locking lever from unlocking the energizing lever when the orientation of the cam is out of the specific angular range of rotation.
Since the energizing lever deactivator prohibits the locking lever from unlocking the energizing lever when the orientation of the cam is out of the specific angular range of rotation in this construction, it is possible to prevent an intense shock which could occur when the energizing lever released from the locking lever turns in its deenergizing direction and hits against the cam.
In another aspect of the invention, the energizing mechanism further includes an electric motor deactivator which prohibits the electric motor from operating when the energizing lever is locked by the locking lever.
Since the energy-storing device is already energized when the energizing lever is locked by the locking lever in this construction, the electric motor is kept from unnecessarily executing energizing operation.
In another aspect of the invention, the retaining device further includes an energizing lever deactivator which prohibits the locking lever from unlocking the energizing lever when the orientation of the cam is out of the specific angular range of rotation, and the energizing mechanism further includes an electric motor deactivator which prohibits the electric motor from operating when the energizing lever is locked by the locking lever.
Since the energizing lever deactivator prohibits the locking lever from unlocking the energizing lever when the orientation of the cam is out of the specific angular range of rotation in this construction, it is possible to prevent an intense shock which could occur when the energizing lever released from the locking lever turns in its deenergizing direction and hits against the cam.
Also, since the energy-storing device is already energized when the energizing lever is locked by the locking lever, the electric motor is kept from unnecessarily executing energizing operation.
In another aspect of the invention, the locking lever is rotatably mounted and maintains the energizing lever in its energized condition when locked by a rotatably mounted closing trigger, the energizing lever is unlocked when the locking lever locked by the closing trigger is released by turning the closing trigger by a swingable member swingably connected to a plunger of an electromagnet, and the energizing lever deactivator includes an operating member which causes the swingable member to swing when pushed by the cam and thereby prevents the closing trigger from turning even when the plunger moves.
In this construction, the swingable member is caused to swing by pushing the operating member with the cam such that the closing trigger is not turned even if the plunger moves when the orientation of the cam is out of the specific angular range of rotation. This makes it possible to prevent an intense shock which could occur when the energizing lever released from the locking lever turns in its deenergizing direction and hits against the cam.
In another aspect of the invention, the electric motor deactivator is a lever switch operated by the energizing lever when the energizing lever is locked by the locking lever.
This makes it possible to cut power supply to the electric motor by means of a simple and low-cost lever switch.
In another aspect of the invention, the braking device is an elastic member having a specific elasticity which elastically deforms and slides over the cam to brake it when the rotating cam reaches the third angular position and pushes the braking device.
By use of the elastic member, it is possible to simplify the construction of the operating apparatus and make it compact and inexpensive.
In another aspect of the invention, the braking device is a leverlike member joined to the energizing lever, wherein the leverlike member is located at a position where it can go into contact with the cam and brake it when the rotating cam reaches the third angular position while the energizing lever is locked by the locking lever, and the leverlike member is located at a position where it does not go into contact with the cam when the energizing lever is released from the locking lever.
In this construction, the energizing lever is released from the locking lever when energizing the energy-storing device. At this time, the leverlike member is located at the position where it does not go into contact with the cam such that the leverlike member does not exert any load on the cam during the energizing operation.
In still another aspect of the invention, the energizing lever of the on-off switch driver includes a first lever section which is connected to the energy-storing device and a second lever section which is connected to the first lever section and turned by the cam.
Since the second lever section is turned when energizing the energy-storing device, it is not necessary to provide the cam and the locking lever around the first lever section. This construction helps increase the degree of freedom of the design of the operating apparatus.
In yet another aspect of the invention, the energy-storing device is a torsion bar which is connected to the energizing lever and elastically deforms when twisted by the energizing lever.
It is possible to make an energy-storing device capable of achieving a high energy efficiency and free of stress concentration by use of a torsion bar.
In a further aspect of the invention, the energy-storing device is a coil spring which is connected to the energizing lever and elastically deforms when compressed or extended by the energizing lever.
This makes it possible to produce a compact energy-storing device.
In a still further aspect of the invention, the cam has a cam surface which produces a generally constant torque applied to the electric motor when the energy-storing device is energized by turning the energizing lever.
In this construction, it is possible to make the torque applied to the electric motor generally constant while the energy-storing device is being energized. As a result, it is possible to reduce maximum torques applied to components of the electric motor and the energizing mechanism.
In a yet further aspect of the invention, the switchgear is a circuit breaker.
The operating apparatus of the invention is suited for use with the circuit breaker.
These and other objects, features and advantages of the invention will become more apparent upon reading the following detailed description in conjunction with the accompanying drawings.